The present invention relates to radio telecommunication systems. More particularly, and not by way of limitation, the present invention is directed to a method and a congestion controller for controlling congestion in a sector of a cellular telecommunication network that is limited by available downlink transmit power.
When excessive traffic in a cellular telecommunication network results in congestion control, the downlink (DL) data rate may be reduced to a lowest retainable rate in an attempt to reduce the congestion level below a stipulated threshold level. If this is not successful, some of the existing calls may be preempted based on their relative priorities and service types. In the current implementation, when congestion is detected, certain non-guaranteed traffic class connections referred to as Air Interface Speech Equivalents (ASEs) are released at periodic intervals followed by Guaranteed ASEs until the congestion is resolved. In an ASE, normally different services like video calls, High Speed Downlink Packet Access (HSDPA) calls, and the like are converted to one unique service like a speech call. This process typically results in a certain number of non-guaranteed as well as guaranteed calls being released, which may not create a good customer experience.
FIG. 1 is a graph of downlink transmit carrier power as a function of time when implementing an existing method of congestion control in a cellular telecommunication network. A first time period (tmInitialG) 11 is the minimum time period after detection of downlink (DL) cell congestion before congestion resolution actions are initiated on guaranteed ASEs in a cell. Only non-guaranteed ASEs are released during the tmInitialG time period. The tmInitialG period may vary between 10 msec to 100,000 msec (100 seconds). A default setting of 3,000 msec (3 seconds) is a reference case setting. The actual setting can deviate from the default setting depending on the required speed to resolve the DL cell congestion situation and the characteristics of the non-guaranteed traffic class services in the network.
A second time period (tmCongActionNg) 12 is the interval between periodic congestion resolution actions on the non-guaranteed ASEs in a cell. The tmCongActionNg period may vary between 500 msec to 100,000 msec (100 seconds). A default setting of 800 msec is a reference case setting. The actual setting can deviate from the default setting depending on the required speed to resolve the DL cell congestion situation and the characteristics of the non-guaranteed traffic class services in the network.
A first parameter (releaseAseDINg) 13 is the number of non-guaranteed ASEs in the DL to be released with each periodic congestion resolution action targeting non-guaranteed ASEs in a cell. The releaseAseDINg parameter may vary between 0 and 500 ASEs. A default setting of 3 ASEs is a reference case setting. The actual setting can deviate from the default setting depending on the required speed to resolve the DL cell congestion situation and the characteristics of the non-guaranteed traffic class services in the network.
Following the expiration of the tmInitialG time period 11, the process may release guaranteed ASEs. A second parameter (releaseAseDI) 14 is the number of guaranteed ASEs in the DL to be released with each periodic congestion resolution action targeting guaranteed ASEs in a cell. The releaseAseDI parameter may vary between 0 and 500 ASEs. A default setting of 1 ASE is a reference case setting. The actual setting can deviate from the default setting depending on the required speed to resolve the DL cell congestion situation and the characteristics of the guaranteed traffic class services in the network.
A third time period (tmCongAction) 15 is the interval between periodic congestion resolution actions on the guaranteed ASEs in a cell. The tmCongAction period may vary between 300 msec to 100,000 msec (100 seconds). A default setting of 2,000 msec (2 seconds) is a reference case setting. The actual setting can deviate from the default setting depending on the required speed to resolve the DL cell congestion situation and the characteristics of the guaranteed traffic class services in the network.
As can be seen, both non-guaranteed and guaranteed services are released in order of priority by releasing ASEs periodically to resolve congestion.